Large quantities of fine-particle solids of high water content accumulate in numerous branches of industry, for example in mining or in sewage treatment plants, and have to be dewatered before further processing or disposal as waste. For example, the dewatering of water-containing hard coal or coke is a central process in the preparation of coal-based fuels. It is often difficult to keep to the upper limits dictated by the market for the water content of these materials, for example because mined hard coal accumulates in very fine-particle form by virtue of the substantial mechanization of underground coal mining. At the present time, around 38% of mine-run coal consists of fine coal with particle diameters ranging from 0.5 to 10 mm; a further 14% consists of very fine coal with even smaller particle diameters.